This invention relates generally to centrifugal compressors and, more particularly, to a method and apparatus for locating a silencer device in the collector of a centrifugal compressor.
Centrifugal compressors, of the type which are used for large air conditioning systems, have a number of included components which create sound and vibration that radiates from the compressor and attached components including the motor, gearing, condenser and evaporator shells and the discharge line. In addition to design considerations that tend to minimize these sounds, it is common practice to reduce the sound by way of external, surface applied lagging materials or the addition of internal discharge line silencers (i.e. and acoustically absorptive material such as fiber glass, mineral fiber, or Dacron) which are placed in the discharge line of the compressor. The usual approach for installing a silencer device in the discharge pipe of a compressor is by securing the entire assembly to the inner sidewalls of the discharge pipe by welding or the like. Because of the relatively small size of the discharge pipe and the desirability for placement of the silencer in axial locations within the pipe, the accessibility is severely limited and thereby complicates the process. Further, when welding is performed in close proximity to the absorptive material within the silencer device, as is usually required, the absorptive material may be damaged by the resulting heat.
Rather than installing a silencer device directly in the discharge pipe, another approach is to remove a portion of the discharge pipe and install a complete replacement section comprising a pipe-like structure with the silencer device installed therein. Such a unit has customarily been attached by way of mating flanges. Such an approach is therefore relatively expensive, involving both extensive expenditures of time and material.
A dominant noise source in most centrifugal chillers is the noise produced in the discharge gas stream by the compressor impeller. It would therefore be desirable to strategically locate a suitable absorbing material such that a large percentage of this noise can be absorbed before it reaches the discharge line. To do so it would be necessary to place absorbing material either in the diffuser or in the discharge chamber commonly referred to as the volute. However, the volute has the same problems of accessibility as does the discharge tube. Not only is it difficult to place the absorptive material within the volute, but it is made more difficult by the need to securely retain the absorptive material in circumferentially spaced locations within the volute. In this regard, in addition to the problem of accessibility as discussed hereinabove, conventional methods of fastening the parts in place are not practical for other reasons. First, the discharge chamber is a pressure containing member so that the forming of holes through the wall for attachment are not desirable. Secondly, the pressure chamber is normally made from cast iron, and welding of cast iron is impractical. Thirdly, the use of an adhesive is difficult because of its likely incompatibility with refrigerant. Finally, the apparatus for retaining any such sound absorbing material within a discharge chamber must be capable of allowing self adjusting or a shifting in the position of the silencer parts as they "bed themselves in" against the relatively rough wall within the discharge chamber.
It is therefore an object of the present invention to provide an improved centrifugal compressor silencer apparatus and method of installation.
Another object of this invention is the provision for securing a silencer device within a discharge chamber of a centrifugal compressor.
Yet another object of the invention is the provision for securing a silencer in the discharge chamber of a centrifugal compressor without the use of welding or adhesives.
Still another object of the present invention is the provision in a centrifugal compressor discharge chamber for allowing a silencer device to "bed itself in" during operation.
Still another object of the present invention is the provision for installing a silencer in a centrifugal compressor in an effective, efficient and economical manner.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.